Compressor of an exhaust-gas turbocharger

ABSTRACT

A compressor ( 8 ) of an exhaust-gas turbocharger ( 1 ), having a compressor wheel ( 11 ) which can be driven in a compressor wheel direction of rotation (VR); having a compressor housing ( 10 ) in which the compressor wheel ( 11 ) is arranged, as viewed in the flow direction of the inducted air, between a preferably tubular compressor inlet ( 12 ) and a compressor outlet ( 13 ), and having an overrun air recirculation valve inflow duct ( 14, 15 ) which runs in the compressor housing ( 10 ) from the compressor outlet ( 13 ) to the compressor inlet ( 12 ), wherein the inflow duct ( 14, 15 ) opens into the compressor inlet ( 12 ) substantially in the circumferential direction with respect to the inner diameter (D I ) of said compressor inlet ( 12 ).

The invention relates to a compressor of an exhaust-gas turbocharger, as per the preamble of claim 1.

In the generic compressor which is provided with an overrun air recirculation valve, the compressor housing has an inflow duct which runs from the compressor outlet to the compressor inlet. Said inflow duct is controlled by the overrun air recirculation valve in order, during operation of the exhaust-gas turbocharger, to prevent a pumping effect which may for example arise when, on account of a braking process of the motor vehicle, the throttle flap is closed but the exhaust-gas turbocharger would still run at high rotational speed. In this situation, to prevent the stated effect, the overrun air recirculation valve is opened and air is conducted from the compressor outlet, or the pressure side, to the compressor inlet, so as to ensure a continuous flow through the compressor wheel without a significant pressure build-up.

In the already known design, the inflow duct runs into the compressor inlet radially, which means that the inflow is directed toward the center of the shaft of the exhaust-gas turbocharger.

Tests carried out within the context of the invention with said design of a known exhaust-gas turbocharger have shown that, on account of the stated opening of the inflow duct radially with respect to the shaft as a result of the inflow direction to the compressor wheel, flow noise is generated which can lead to undesired noise disturbance during the operation of a vehicle provided with an exhaust-gas turbocharger of said type.

In contrast, it is an object of the present invention to provide a compressor of the type specified in the preamble of claim 1, which compressor makes it possible to avoid or considerably reduce the explained flow noises, and also dampen any occurring resonances.

Said object is achieved by means of the features of claim 1.

According to said claim, the inflow duct is arranged in the compressor housing in such a way as to open into the compressor inlet at least in the circumferential direction with respect to a tube inner diameter of the tubular compressor inlet. Said opening may also be referred to as an at least substantially tangential opening, which leads to a tangential inflow, or an inflow directed in the circumferential direction, of the air recirculated from the pressure side into the inducted air, which inflow has at least substantially no disruptive influence on the compressor wheel and therefore reduces the flow noises explained in the introduction at least to such an extent that the noises are practically no longer perceptible.

The inflow directed substantially in the circumferential direction may also have an axial component directed in the flow direction in order to reduce inflow losses.

For this purpose, the compressor inlet may be provided with a cylindrical or frustoconical inflow section into which the inflow duct opens in the way explained above.

The subclaims relate to advantageous refinements of the invention.

In a particularly preferred embodiment, the inflow duct opens into the compressor inlet in such a way that the inflow of the recirculated air leads in the direction of rotation of the compressor wheel. An inflow counter to the direction of rotation of the compressor wheel is, however, also possible in principle.

Further details, advantages and features of the present invention will emerge from the following description of exemplary embodiments on the basis of the drawing, in which:

FIG. 1 shows a perspective, partially cut-away illustration of an exhaust-gas turbocharger which may be provided with a compressor according to the invention,

FIGS. 2, 3 show a first embodiment of a compressor according to the invention, and

FIG. 4 shows a second embodiment of a compressor according to the invention.

FIG. 1 illustrates an exhaust-gas turbocharger 1 according to the invention which has a turbine housing 2 comprising an exhaust-gas inlet opening 3 and an exhaust-gas outlet opening 4.

Furthermore, a turbine wheel 5 is arranged in the turbine housing 2, which turbine wheel is fastened to a shaft 6.

A multiplicity of blades, of which only the blade 7 is shown, is arranged in the turbine housing 2 between the exhaust-gas inlet opening 3 and the turbine wheel 5.

Furthermore, the exhaust-gas turbocharger 1 has a compressor 8, the compressor housing 10 of which is in the usual way connected via a bearing housing 9 to the turbine housing 2. In the compressor housing 10, a compressor wheel 11 is fastened to the second end of the shaft 6. The details of the compressor 8 according to the invention will be explained below on the basis of FIGS. 2 to 4, which illustrate two embodiments of the compressor 8 according to the invention which may be used in the exhaust-gas turbocharger 1 illustrated in FIG. 1.

The embodiment according to FIGS. 2 and 3 clearly shows in FIG. 2 the compressor wheel by the three plotted arrows VR together with the label “direction of rotation VR”, which symbolizes the compressor wheel 11 with its associated direction of rotation. The compressor wheel 11 is shown in FIG. 3 and is arranged on the shaft 6.

In FIG. 2, the inflow duct of the overrun air recirculation valve (not visible in the figures) is denoted by the reference numeral 14, with said inflow duct 14 opening along the two dashed directions approximately in the circumferential direction or tangentially with respect to the inner diameter (see FIG. 4, D_(I)). Here, FIG. 3 clearly shows an inflow duct opening 16 which opens into a tubular or funnel-shaped or frustoconical funnel inlet 12, in such a way as to permit a tangential inflow of the air recirculated from the compressor outlet 13. As is clearly shown in FIGS. 2 and 3, the inflow here runs counter to the direction of rotation VR.

The dash-dotted parallel lines which are additionally shown in FIG. 2 and which are identified by the reference symbol ZK serve merely to clearly show the arrangement of the inflow duct according to the prior art. Said illustration of the dashed lines ZK clearly shows an arrangement of the inflow duct radially with respect to the shaft 6, which is associated with the problems explained in the introduction. Here, it is mentioned once again that said additional plotting of the known inflow duct ZK in FIG. 2 serves merely to clearly show the differences between the prior art and the invention; such an inflow duct ZK is not provided in the compressor according to the invention either in the embodiment according to FIGS. 2 and 3 or in the embodiment according to FIG. 4.

FIG. 4 shows a second embodiment of the compressor 8 according to the invention, which like the embodiment according to FIGS. 2 and 3 self-evidently has a compressor housing 10 with a compressor inlet 12 (not visible in the selected illustration) and a compressor outlet 13. The inflow duct 15 likewise indicated in FIG. 4 by means of dashed lines has a first, rectilinearly running duct section 15 a and, adjoining the latter, a bent duct section 15 b which results in the above-explained opening aligned tangentially, or substantially in the circumferential direction, with respect to the inner diameter D_(I) of the compressor inlet 12. Here, the opening takes place such that the inflow of recirculated air runs in the direction of rotation VR of the compressor wheel 11, which is likewise symbolized by the arrow YR in FIG. 4.

Aside from the written disclosure of the invention, reference may additionally be made to the graphic illustration thereof in FIGS. 1 to 4, in particular in FIGS. 2 to 4.

LIST OF REFERENCE SYMBOLS

-   1 Exhaust-gas turbocharger -   2 Turbine housing -   3 Exhaust-gas inlet opening -   4 Exhaust-gas outlet opening -   5 Turbine wheel -   6 Shaft -   7 Blade -   8 Compressor -   9 Bearing housing -   10 Compressor housing -   11 Compressor wheel -   12 Compressor inlet -   13 Compressor outlet -   14 Overrun air recirculation valve inflow duct -   15 Overrun air recirculation valve inflow duct -   15 a, b Duct sections -   16 Duct opening -   ZK Inflow duct of the prior art -   VR Direction of rotation of the compressor wheel 11 -   D_(I) Inner diameter of the compressor inlet 12 

1. A compressor (8) of an exhaust-gas turbocharger (1), having a compressor wheel (11) which can be driven in a compressor wheel direction of rotation (VR); having a compressor housing (10) in which the compressor wheel (11) is arranged, as viewed in the flow direction of the inducted air, between a compressor inlet (12) and a compressor outlet (13), and having an overrun air recirculation valve inflow duct (14, 15) which runs in the compressor housing (10) from the compressor outlet (13) to the compressor inlet (12), wherein the inflow duct (14, 15) opens into the compressor inlet (12) substantially in the circumferential direction with respect to the inner diameter (D_(I)) of said compressor inlet (12).
 2. The compressor as claimed in claim 1, wherein the inflow duct (15) opens into the compressor inlet (12) in such a way that the inflow of air takes place in the direction of rotation (VR) of the compressor wheel (11).
 3. The compressor as claimed in claim 1, wherein the inflow duct (14) opens into the compressor inlet (12) in such a way that the inflow of air takes place counter to the direction of rotation (VR) of the compressor wheel (11).
 4. The compressor as claimed in claim 1, wherein the inflow duct (14) opens into the compressor inlet (12) in such a way that the inflow of air has an axial component in the flow direction.
 5. The compressor as claimed in claim 1, wherein compressor inlet (12) is tubular. 